<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
<select name="" id="city">
    <option value="">河南</option>
    <option value="">河北</option>
    <option value="">湖南</option>
    <option value="">江南</option>
</select>
<script>
var city=document.getElementById('city');
city.onchange=function(){
    console.log(1);
}
</script>
</body>
</html>